Thread control device for a textile machine, in particular for a shedding device

ABSTRACT

The invention relates to a thread control device for a textile machine, in particular, for a shedding device, with at least one thread guide body ( 31 ) which may be displaced in one displacement direction by means of a positive drive ( 35 ) and in the opposite direction by means of a non-positive, pneumnatic return device ( 36 ). Me return device ( 36 ) thus comprises a cylinder/piston unit ( 64,54 ), the cylinder chamber of which ( 52 ) is connected to a compressed gas source ( 60 ) by means of a valve ( 56 ). An improvement in control is achieved when the valve ( 56 ) comprises a first valve seat ( 72 ) connected to the cylinder chamber ( 52 ) and a second valve seat ( 76 ), between which a valve body ( 82 ), provided with at least one throttle point ( 80 ), may be displaced, pre-tensioned in the rest position by means of a spring ( 84 ) against the first valve seat ( 72 ), in which the throttle point ( 80 ) is ineffective and the valve body ( 82 ) blocks the communication with the compressed gas source ( 60 ) when the valve body ( 82 ) is in contact with the second valve seat ( 76 ).

TECHNICAL FIELD

The invention relates to a thread control device for a textile machine,in particular for a shedding device, according to the preamble of claim1.

PRIOR ART

Large numbers of thread control devices for textile machines are known.The nearest prior art according to WO 97/08373 discloses a threadcontrol device which is designed with a drive and with a return devicefor a thread guide member. The thread guide member is in this casemoveable in one direction of movement by means of the positivelydesigned drive and in the opposite direction of movement by means of anonpositive and pneumatically designed return device acting counter tothe positive drive.

The pneumatic return device has a cylinder/piston assembly, the cylinderchamber of which is designed with an excess pressure valve and with anon-return valve which is connected to a compressed gas source. The gaspressure in the cylinder chamber is in this case set as a function ofthe operating state of the textile machine. For example, in acreep-speed phase, the gas pressure is kept lower than in a high-speedphase, so that the electric motor can furnish the necessary power forovercoming the load occurring as a result of the compression of thecylinder chamber. In a high-speed phase, the electric motor deliverssufficient power, so that the gas pressure can be increased further inorder to prevent a roller on a cam disk of the positive drive fromlifting off. Furthermore, the cylinder chamber may be designed with amanually actuable pressure relief valve, in order, when the textilemachine is being set up, to minimize the resistance occurring as aresult of the compression in the cylinder chamber.

The above solution has the disadvantage that the gas pressure in thecylinder chamber has to be adapted to a respective operating state. Thisnecessitates a complicated pressure control device for setting the gaspressure of the cylinder chamber, which requires pressure reducingvalves and opening valves for activating each cylinder chamber.Moreover, a complicated electronic control of the valves is necessary inorder to adapt the pressure in the cylinder chambers to a respectiveoperating state.

To lubricate the cylinder/piston assembly, oil drops onto the piston,for example from above, and, due to hydrodynamic effects, enters thecylinder chamber despite a permanent excess pressure in the latter. Theoil which has accumulated in the cylinder chamber may persistentlydisrupt the operation of the thread control device, since it reduces theair volume in the cylinder chamber to an indeterminate level, thusleading, during operation, to higher incalculable compression pressuresin the chamber. In an extreme case where a large part of the cylinderchamber is filled with oil, it is no longer possible for the cylinder tomove and further operation of the textile machine would lead toconsiderable damage.

In an improved embodiment of the pneumatic return device described in WO97/08373, therefore, the valve is designed in such a way that oilseparation is also possible in addition to the requirements ofstationary operation. The valve is in this case actuated at regular timeintervals for a few seconds so as to cause the oil which has accumulatedin the compression space to flow out. So that a lifting off of theroller from the eccentric of the positive drive is avoided, therotational speed of the textile machine has to be reduced during thisaction (what is known as the care cycle). At creep speed, said valve islikewise opened, so that the pressure in the cylinder chamber does notrise appreciably above the feed pressure. The required power of themotor is thereby reduced, which is necessary so that the main motor canrotate at low rotational speeds and therefore manual rotation on thehand wheel is possible without excessive effort.

The disadvantage of the above solution is the high outlay for theelectrical/pneumatic activation of the valve. The entire control of thepneumatic drive of the thread control device therefore has a largenumber of components, such as non-return valves, excess pressure valves,pressure reducing valves, and also electronic control units which makethe system more susceptible to faults. Moreover, the efficiency of thetextile machine is reduced as a result of the repetitive lowering of themotor rotational speed in order to discharge the lubricating oil, thislowering taking place every 15 minutes. Furthermore, this lowering ofthe motor rotational speed may have an adverse influence on weavingquality, for example may lead to a slight change in the width of thecloth web produced.

PRESENTATION OF THE INVENTION

The object of the invention is to improve a thread control device of thetype that has been mentioned initially.

The set object is achieved by means of the characterizing features ofclaim 1. Since the valve has a first valve seat connected to a cylinderchamber, and has a second valve seat, between which a valve memberprovided with at least one throttle point and prestressed against thefirst valve seat by means of a spring is moveable, the throttle pointbeing inactive and the valve member shutting off communication with thecompressed gas source when the valve member is against the second valveseat, the valve can operate in various operating states without externalactivation. Furthermore, reliable oil separation is ensured, withoutadditional measures, by the independently operating valve, without alowering of the rotational speed, a reduction of the maximum compressionpressure in the cylinder chamber under part load and a lowering of thecompression pressure to the feed pressure at creep speed.

Advantageous refinements of the invention are described in claims 2 to19.

In principle, the most diverse embodiments to the valve designed withtwo valve seats may be envisaged. A refinement as claimed in claims 2and 3 is advantageous, according to which the housing has two parts, onepart having at one end the first valve seat and the other part beingdesigned as a closing-off part of the housing with a second valve seatand with a passage duct. The valve therefore has as simple aconstruction as possible, which allows cost-effective production andsimple assembly of the valve.

The valve housing may, in principle, have various forms, a cylindricaldesign of the housing according to claim 4 being advantageous. Thisdesign allows a good guidance of the piston-like valve member in thehousing. Moreover, the piston-like valve member may be provided with asealing ring in order to seal off the cylinder chamber outwardly. In theversion according to claim 4, it is advantageous to design the throttlepoints as throttle orifices formed on the valve member. According toclaim 5, it is also conceivable to design the valve member without asealing ring, in which case a gap between the valve member and thehousing wall may serve as a throttle point.

The valve may be arranged in a connecting line between the cylinderchamber and the feed pressure chamber. However, a direct arrangement inthe cylinder of the cylinder/piston assembly according to claim 6 isadvantageous. Furthermore, according to claim 7, it is advantageous toarrange the valve at a lowermost point of the cylinder. The valve canthus communicate directly with the cylinder chamber, and lubricating oilwhich has accumulated in the cylinder chamber can thus be led along ashort path through the valve into the feed pressure chamber.Correspondingly, the closing-off part of the valve is connected directlyto the feed pressure chamber according to claim 8, in order, again, tominimize the flow resistance and the flow path of the out-flowing oil.

The feed pressure chamber may, in principle, be of any desired design. Adesign as claimed in claims 9 to 12 is advantageous, according to whichthe feed pressure chamber may be designed with an oil separation outletarranged at its bottom and according to which a connection forcompressed air may be arranged, at a distance from the bottom of thefeed pressure chamber, on a lateral wall. This arrangement of acompressed air connection and oil separation outlet prevents oil whichhas accumulated in the feed pressure chamber from blocking thecompressed air connection or from flowing in in a connecting line of thecompressed air connection. In principle, any return device may have aseparate feed pressure chamber. It is advantageous, however, accordingto claim 12, to connect a plurality of return devices to one feedpressure chamber. A simple construction with only one connection forcompressed air and with only one oil separation outlet for a pluralityof return devices is thereby possible.

In principle, the most diverse designs of the pneumatic return deviceaccording to the invention may be envisaged. In claims 13 to 16, aparticularly simple design of the valve is described, in which, inconjunction with claims 5 and 6, the valve may be arranged at a lowerpoint of the cylinder chamber of the cylinder/piston assembly. Accordingto claim 13, a lower portion of the cylinder may serve as a housing forthe valve. The valve space may advantageously be delimited by thecylinder inner face, by a closing-off part closing off the cylinderchamber and by a valve member and be connected directly to a compressedgas source via a connection arranged on the cylinder wall. A first valveseat for the valve member may be formed, according to claim 14, on anannular stop. According to claim 15, a second valve seat may be formedon a sleeve part of the closing-off part. When the valve member movesagainst the second valve seat, the communication of the cylinder chamberwith the compressed gas source is shut off and the throttle points onthe valve member become inactive. Moreover, it is particularlyadvantageous, according to claim 16, to arrange an oil separation outletdirectly on the closing-off part.

The valve is activated as soon as the pressure in the feed pressurechamber overshoots the switching pressure. The latter depends both onthe pressure in the feed pressure chamber and on the prestressing forceof the spring. A refinement as claimed in claims 17 and 18 isadvantageous, according to which the prestressing force can be set fromoutside, for example, via a screw.

The maximum compression pressure of the valve can be set, according toclaim 19, by means of the flow cross section of the throttle point. If ahigher compression pressure is required, the flow cross section of thethrottle point is reduced. Owing to the smaller throttle area,communication between the cylinder chamber and the compressed gas sourceis interrupted earlier, thus achieving a higher maximum compressionpressure.

By means of the versions according to claims 17 to 19, the switchingpressure and the maximum compression pressure in the cylinder chambercan be set in a simple way.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the thread control device of the invention aredescribed in more detail below, for a needle-type ribbon weavingmachine, by means of the drawings, in which:

FIG. 1 shows a needle-type ribbon weaving machine in a side view;

FIG. 2 shows a healed frame device with pneumatic return device in aview transverse to the running direction of the warp threads;

FIG. 3 shows the pneumatic return device illustrated in FIG. 2 as adetail and on a larger scale in the basic position;

FIG. 4 shows the pneumatic return device illustrated in FIG. 3 in thecompression position;

FIG. 5 shows a further exemplary embodiment of a pneumatic return deviceon a larger scale;

FIG. 6 shows the pneumatic return device illustrated in FIG. 5 in thecompression position;

FIG. 7 a shows pressure and piston profiles of the pneumatic returndevice according to the invention at creep speed;

FIG. 7 b shows pressure and piston profiles of the pneumatic returndevice under part load; and

FIG. 7 c shows pressure and piston profiles of the pneumatic returndevice under full load.

WAYS OF IMPLEMENTING THE INVENTION

FIG. 1 shows a needle-type ribbon weaving machine with a machine stand2, in which is mounted a main drive shaft 4 which drives at least oneweft needle 6, not described in any more detail, a reed 7, a clothtake-up 8 and a thread control device formed as a healed frame device10. The needle-type ribbon weaving machine has a warp beam stand 12carrying warp beams 14, from which warp threads 16 are supplied to thehealed frame device 10 which opens the warp threads to form a shed 18.By means of a thread supply device 20, a weft thread 24 is supplied froma thread bobbin 22 to the weft needle 6 which introduces a weft threadloop into the shed 18. Successive weft thread loops can be tied off withthemselves or by means of a tucking thread 26 which is supplied via afurther thread supply device 28 to a knitting needle, not illustrated inany more detail here, in order to tie off and secure an inserted weftthread loop.

FIG. 2 shows the healed frame device 10, in which a plurality of healedframes 30 with thread guide members 31 are connected in each case bymeans of a link 32, on the one hand, via a positive drive 35, to a camdrive 34 and, on the other hand, to a pneumatic return device 36. Thecam drive 34 has pivoting levers 38 which cooperate at a drive point 40with cams 42 of a camshaft 44. At the output point 46, the pivotinglevers 38 are articulated on the links 32 via joints 48. The pivot axesdefined by the joints 48 run at right angles with respect to the planesspanned by the healed frames 30. The distances A of the pivoting levers38 of the drive points 40 from the respective pivot axes 50 aredifferent between adjacent pivoting levers, the distances B of theoutput points 46 from the fixed pivot axes 50 also being different, suchthat, overall, the healed frames are displaceable over extents ofdifferent size, in order to form a shed continuously widening andnarrowing again, as may be gathered from FIG. 1. The pneumatic returndevice 36 is formed by a cylinder chamber 52, in which a piston 54 isdisplaceable, which is connected to the link 32, in order to compressthe piston positively at the working frequency of the cam drive 34. Thecylinder chamber 52 is connected to a valve 56. The latter is precededby a feed pressure chamber 58, via which a compressed gas source 60 isconnected, in order to maintain the gas pressure in the cylinder chamber52.

FIG. 3 and FIG. 4 show the pneumatic return device on a larger scaleduring a compression action. In this case, FIG. 3 illustrates the piston54 at a top dead center 66, and FIG. 4 illustrates the piston 54 at abottom dead center 68 in a cylinder 64 after compression. The valvehousing consists of two parts, a sleeve-like housing 70 with a firstvalve seat 72, formed at one end and connected to the cylinder chamber52, and a closing-off part 74 which has a second valve seat 76 and apassage duct 78. The latter is connected to the feed pressure chamber58. A valve member 82 provided with throttle points 80 is arrangedmoveably between the valve seats.

In the initial state shown in FIG. 3, the valve member 82 is prestressedagainst the first valve seat 72 by means of the prestressing force ofthe spring 84, so that the cylinder chamber 52 and the feed pressurechamber 58 are in communicating connection with one another via thethrottle points 80 in the valve member 82 and the passage duct 78 of theclosing-off part 74. In the case of a high pressure in the cylinderchamber 52, the valve member 82 moves against the second valve seat 76and interrupts communication between the cylinder chamber 52 and thefeed pressure chamber 58, as illustrated in FIG. 4. The throttle points80 are inactive in this position.

The compression/expansion action of the cylinder/piston assembly isdescribed below by means of FIGS. 3 and 4 and in conjunction with thegraphs of FIGS. 7 a, 7 b and 7 c. In the latter, H stands for the strokeof the piston of the cylinder/piston assembly, with UT as bottom deadcenter and OT as top dead center, and PK stands for the pressure of thegas in the cylinder chamber. PS represents the necessary switchingpressure so that the valve member switches from the first valve seat tothe second or from the second valve seat to the first. The switchingpressure PS can be divided into the feed pressure PD of the compressedgas source and the corresponding pressure PF of the spring force. VZ inthis case illustrates the position of the shut-off valve and VOillustrates the position of the valve communicating with the cylinderchamber via the throttle points.

First, the piston 54 moves in the cylinder 64 from the top downward andat the same time, in a first phase, displaces air through the throttlepoints 80 formed on the piston-like valve member 82, toward the feedpressure chamber 58. As the piston speed increases, the pressuredifference (PK-PD) across the valve member 82 rises, until the switchingforce generated by the cylinder chamber pressure PK on the valve member82 overcomes the prestressing force of the spring 84 and the force onthe valve member 82 generated by the feed pressure PD, and presses thevalve member 82 against the second valve seat 76. The throttle point 80of the valve member 82 is then no longer active. By the piston 54 beingmoved further toward the valve 56, therefore, the cylinder chamberpressure PK rises sharply during the compression action in the cylinderchamber 52 and reaches its maximum at bottom dead center UT. In theexpansion phase, the valve member 80 moves from the second to the firstvalve seat 76 as soon as the spring force overshoots the force generatedon the valve member 80 as a result of the pressure difference (PK-PD).At the end of the expansion phase, corresponding to the top dead center66 of the piston, the feed pressure PD is established in the cylinderchamber. Moreover, any oil which has accumulated in the cylinder chamber52 can then flow out through the passage duct 78. During the nextcompression action, the out-flowing oil is blown out by the airdisplaced into the feed pressure chamber 58 and flows out in an oilseparation outlet 88 formed on a bottom 86 of the feed pressure chamber.A connection 90 for compressed air is arranged on a lateral wall 92 ofthe feed pressure chamber and consequently prevents a further backflowof the oil.

FIG. 5 and FIG. 6 show a further design variant of a pneumatic returndevice on a larger scale during a compression action. In this case, FIG.5 again illustrates the piston 54 at a top dead center 66, and FIG. 6illustrates the piston 54 at a bottom dead center 68 in the cylinder 64after compression of the cylinder chamber 52. A valve 56 a is againarranged directly at the lowermost point of the cylinder 64. The wall ofthe cylinder in this case serves as a valve housing, and a valve space94 is delimited by the wall of the cylinder 64, a closing-off part 74 aclosing off the cylinder 64, and a piston-like valve member 82 a. A stop71 designed as a ring is arranged directly inside the cylinder 64 of thecylinder/piston assembly and serves as a first valve seat 72 a for thepiston-like valve member 82 a. The latter is again prestressed againstthe first valve seat 72 a by means of a spring 84 a. The spring 84 a isin this case supported on the closing-off part 74 a which closes off thecylinder and has an inner sleeve part 96 for guiding the spring 84 a andthe free end of which serves, moreover, as a second valve seat 76 a forthe valve member 82 a. When the latter butts against the second valveseat 76 a, throttle points 80 a formed in the valve member 82 a becomeinactive. Likewise, in this position, a connection 90 a, arranged on thecylinder, for a compressed gas source 60 is shut off by means of thevalve member 82 a. Oil which has accumulated in the cylinder chamber 52can flow out via an oil separation outlet 88 a formed on the closing-offpart 74 a.

In the initial state shown in FIG. 5, the valve member 82 a isprestressed against the first valve seat 72 a by means of theprestressing force of the spring 84 a, so that the cylinder chamber 52is connected to a compressed gas source via the throttle points 80 a inthe valve member 82 a. In the case of a high pressure in the cylinderchamber 52, the valve member 82 a moves against the second valve seat 76a and interrupts communication between the cylinder chamber 52 and thecompressed gas source 60 by shutting off the connection 90 a arranged inthe cylinder wall, as illustrated in FIG. 6. The throttle points 80 aare inactive in this position.

At the end of an expansion phase, feed pressure is established in thecylinder chamber 52. Any oil which has accumulated in the cylinderchamber 52 can then flow out into the valve space 94 through thethrottle points 80 a. During the next compression action, theout-flowing oil is blown out by the air displaced into the valve space94 and flows out in the oil separation outlet 88 a formed on a bottom 98at the closing-off part 74 a. The connection 90 a for compressed air isarranged, at a distance from the bottom of the closing-off part, on awall 100 of the cylinder and consequently prevents a further backflow ofthe oil. FIGS. 7 a, 7 b and 7 c illustrate the pressure and pistonprofiles of the return device according to the invention over two loadcycles at creep speed for a speed of 800 rev/min (FIG. 7 a), for partload at 1000 rev/min (FIG. 7 b) and for full load at 4000 rev/min (FIG.7 c).

At creep speed to an operating speed of, for example, 800 rev/min (FIG.7 a), continuous pressure compensation takes place via the throttlepoints of the valve member, so that the cylinder pressure PK does notreach the switching pressure PS necessary for interrupting communicationbetween the cylinder chamber and the compressed gas source. The pressurein the cylinder chamber PK is therefore always of the order of magnitudeof the feed pressure PD. The motor load occurring due to the pneumaticdrive is consequently low and allows the motor to run quietly and,particularly with the drive switched off, a movement of the threadcontrol device by hand, for example for setting and repair purposes.

Under part load at 1000 rev/min (FIG. 7 b), the cylinder chamberpressure PK reaches the necessary switching pressure PS during a cycle,whereupon the valve shuts off communication of the compressed gas sourcewith the cylinder chamber and commences compression in the closed-offcylinder chamber. The compression of the cylinder chamber reaches itsmaximum at a bottom dead center UT. During the subsequent expansion, thecylinder chamber pressure PK falls below the switching pressure PSagain. The cylinder chamber is then connected once more to thecompressed gas source, and, when a top dead center OT of the piston isreached, the feed pressure PD is established once again in the cylinderchamber. The compression pressure in the cylinder chamber prevents theroller from being lifted off from the eccentric of the positive drive athigher operating speeds.

Under full load at 4000 rev/min the necessary switching pressure PS isreached earlier (FIG. 7 c) than at lower operating speeds. Compressiontherefore takes place over a larger stroke, and the maximum compressionpressure consequently reaches a higher value than at lower operatingspeeds. During the subsequent expansion, the necessary switchingpressure PS is reached again, whereupon the valve restores thecommunication of the cylinder chamber with the compressed gas source.The maximum compression pressure is a direct function of the speed ofthe machine, that is to say, at a higher speed, the maximum compressionpressure also increases. This is advantageous both for an efficientoperation of the machine and for a satisfactory functioning of thepositive drive.

By the valve being opened once per work cycle, a continuous outflow ofthe lubricating oil which has accumulated in the cylinder chamber takesplace. A reliable and continuous operation of the plant is consequentlypossible, without any maintenance cycles for removing the lubricatingoil from the cylinder chamber. The tasks and requirements for the valvewhich are described above take place independently, that is to saywithout any external activation. The dimensioning of the spring force,of the throttle cross section and of the valve member outside diameteror valve seat diameters affords the independent control functions of thevalve.

The return device described here for a thread control deviceconsequently fulfills the most diverse requirements independently and atthe same time has the least possible outlay in technical terms. Thereturn device can therefore be produced particularly cost-effectivelyand, owing to its simple construction, is largely maintenance-free andfault-free during operation.

The thread control device according to the invention may also be usedfor individual thread control, for example for a Jacquard machine,furthermore, in a weft thread device for the presentation of individualweft threads.

List of Reference Symbols

-   2 Machine stand 56 a Valve-   4 Main drive shaft 58 Feed pressure chamber-   6 Weft needle 60 Compressed gas source-   7 Reed 64 Cylinder-   8 Cloth take-up 66 Top dead center-   10 Healed frame device 68 Bottom dead center-   12 Warp beam stand 70 Housing-   14 Warp beam 71 Stop-   16 Warp thread 72 First valve seat-   18 Shed 72 a First valve seat-   20 Thread supply device 74 Closing-off part-   22 Thread bobbin 74 a Closing-off part-   24 Weft thread 76 Second valve seat-   26 Tucking thread 76 a Second valve seat-   28 Thread supply device 78 Passage duct-   30 Healed frame 80 Throttle point-   31 Thread guide member 80 a Throttle point-   32 Link 82 Valve member-   34 Cam drive 82 a Valve member-   35 Positive drive 84 Spring-   36 Return device 84 a Spring-   38 Pivoting lever 86 Bottom-   40 Drive point 88 Outlet-   42 Cam 88 a Outlet-   44 Cam shaft 90 Connection-   46 Output point 90 a Connection-   48 Joint 92 Wall-   50 Pivot axis 94 Valve space-   52 Cylinder chamber 96 Sleeve part-   54 Piston 98 Bottom-   56 Valve 100 Wall

1. A thread control device for a textile machine, in particular for ashedding device, said thread control device comprising: at least onethread guide member which is moveable in one direction of movement bymeans of a positively designed drive and in the opposite direction ofmovement by means of a nonpositive and pneumatically designed returndevice, the latter having a cylinder/piston assembly the cylinderchamber of which is connected to a compressed gas source via a valve,wherein the valve has a first valve seat connected to the cylinderchamber and a second valve seat between which a valve member, providedwith at least one throttle point is moveable, which valve member, in thebasic position, is prestressed against the first valve seat by means ofa spring, the throttle point being inactive and the valve membershutting off communication with the compressed gas source when the valvemember is against the second valve seat.
 2. The thread control device asclaimed in claim 1, wherein the valve has a housing at one end of whichthe first valve seat is formed.
 3. The thread control device as claimedin claim 2, wherein the second valve seat is formed on a closing-offpart designed with a passage duct.
 4. The thread control device asclaimed in claim 2 wherein the housing is designed cylindrically, inwhich the piston-like valve member is guided, sealed off with respect tothe housing wall.
 5. The thread control device as claimed in claim 2,wherein a gap between the valve member and the housing wall of the valveserves as a throttle point.
 6. The thread control device as claimed inclaim 1, wherein the valve is arranged in the cylinder chamber.
 7. Thethread control device as claimed in claim 1, wherein the valve isarranged in the lowermost point of the cylinder.
 8. The thread controldevice as claimed in claim 1, wherein a closing-off part of the valve isconnected directly to a feed pressure chamber.
 9. The thread controldevice as claimed in claim 8, wherein the feed pressure chamber has anoil separation outlet for oil coming from the cylinder chamber.
 10. Thethread control device as claimed in claim 9, wherein the oil separationoutlet is arranged on a bottom of the feed pressure chamber.
 11. Thethread control device as claimed claim 10, wherein a connection forcompressed air is arranged, at a distance from the bottom of the feedpressure chamber on a lateral wall of the feed pressure chamber.
 12. Thethread control device as claimed in claim 8, wherein the feed pressurechamber of at least one return device serves as a feed pressure and oiloutflow device.
 13. The thread control device as claimed in claim 1,wherein a lower portion of the cylinder serves as a valve housing andhas a connection for the compressed gas source.
 14. The thread controldevice as claimed in claim 13, wherein an annular stop is arrangedinside the cylinder and is designed as a first valve seat connected tothe cylinder chamber.
 15. The thread control device as claimed in claim14, wherein the cylinder is closed off by means of the closing-off part,the latter having a sleeve part the free end of which serves as a secondvalve seat.
 16. The thread control device as claimed in claim 15,wherein an oil separation outlet is arranged on the closing-off part.17. The thread control device as claimed in claim 1, wherein theswitching pressure of the valve can be set by a change in theprestressing force of the spring.
 18. The thread control device asclaimed in claim 17, wherein the prestressing force of the spring can beset from outside.
 19. The thread control device as claimed in claim 1,wherein the maximum compression pressure in the cylinder chamber can beset by means of the flow cross section of the throttle point.
 20. Thethread control device as claimed in claim 3, wherein the housing isdesigned cylindrically, in which the piston-like valve member is guided,sealed off with respect to the housing wall.